This invention relates to cobalt-containing precious metal material employed for the manufacture of decorated articles, personal ornaments, glass frames, keys and the like, and a process for manufacturing the material.
Heretofore, in order to manufacture decorated articles or personal ornaments, such as glass frames, keys and the like, Ag-type, Au-type, Au-Ag-Cu ternary alloys and Pt-type materials have been employed. The Ag-type materials exhibit a color represented by a unique white brightness or a silvery color, while the Au-type materials, such as Au-Ag-Cu ternary alloys are capable of obtaining only a simple hue represented by white, yellow and red. The Pt-type material is comparable to the Ag-type materials in near brightness at the equivalent thickness levels although not as decorative as the Au-type materials.
These days the materials that are employed for the above uses, require peculiar colors which have not previously existed. In addition to satisfying the needs of fashion, design and intrinsic decorative effects achieved by the materials, account must be taken of the costs of the metals and their availability.
In order to comply with such a need, some attempts have been conventionally made to bring out blackish gray by means of a sulfide film and blue by means of an oxide film on an Au-Fe (24%) alloy, but no practical uses have been realized.
Precious metals usually have bright colors, and no precious metal materials having black appearance have been known. The precious metal materials having black appearance were developed, they could have a great impact on the precious metal industry.